Most up to date electric fans include a large number of small components which are generally awkward and time consuming to fit in the fan. Added to this is the fact that some fan constructions have now gone to a combination heater and fan further increasing the number of components in the construction.
In most fan assemblies, the many components each require their own set screw or the like to hold that particular component in position while the rest of the fan is being assembled. This adds further to the cost of the fan whether it be a conventional or a heater fan from both a labour standpoint and a material standpoint because of the costs of the set screws themselves.